Method and device for enhancing vessel occlusion

ABSTRACT

Body lumens such as blood vessels are selectively occluded by applying radiofrequency voltage to a vaso-occlusive coil ( 100 ) at the target site (TS) and generating a thermal reaction to induce fibrogenic occlusion of the blood vessel (BV) around the vaso-occlusive coil. The radiofrequency current is usually sufficient to induce thermal damage to the luminal wall and to coagulate the surrounding blood, thereby initiating clotting and subsequent fibrosis to permanently occlude the lumen. The invention also includes a method for endoluminally deploying the vaso-occlusive coil and preventing migration of the coil from of the target site.

This application is a continuation of U.S. patent application Ser. No.08/605,765, filed Feb. 22, 1996, now issued as U.S. Pat. No. 6,270,495,the entire disclosure of which is expressly incorporated by referenceherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to methods and devices for theselective occlusion of body lumens. More particularly, the presentinvention relates to methods and devices for applying high frequencyelectrical energy to vaso-occlusion elements within the body lumen toenhance fibrogenic occlusion of the body lumen.

The selective occlusion of blood vessels in a patient is a part of manymodem therapeutic treatments, including the control of internalbleeding, the occlusion of blood supply to tumors, the isolation ofdiseased body organs prior to removal, the relief of blood pressure in aregion of aneurism, and the like. While such procedures rely generallyon the blockage of arteries, the selective occlusion of veins is alsouseful in procedures such as veiniotomy.

The selective occlusion of blood vessels can be achieved by a variety ofspecific techniques. One such technique involves mechanically clampingor occluding the target site within the blood vessel. For example, inopen surgical and endoscopic procedures, the body vessel can beexternally clamped and radiofrequency energy applied. While the externalprocedures can be very effective, it requires external access to thelumen and is unsuitable for endoluminal techniques.

Mechanical endoluminal techniques for selective vessel occlusion arealso in use. Such techniques include the use of detachable balloons,embolic and vaso-occlusion coils, and the like to physically block thevessel lumen. Detachable balloons are typically advanced to the vesselsite at the end of a catheter and inflated with a suitable fluid, suchas saline, x-ray contrast or a polymerizable resin, and released fromthe end of the catheter. These detachable balloons, however, aredifficult to deliver and may not be suitable for permanent implantationunless they are used with the polymerizable resin. In addition, thecatheter or the balloon can rupture or release prematurely duringfilling, leaking monomer resin into the vasculature.

Embolic or vaso-occlusion coils are typically introduced through acatheter in a stretched linear form, and assume a relaxed, helical shapewhen released into a vessel. One of the limitations of these coils isthat recanalization of the occlusion site can occur when the initialblood clot is broken down by the body's natural anticoagulant mechanism(i.e., resorption of the clot). In addition, once the embolic coils arereleased by the introducer catheter, they are no longer under controland they frequently migrate from the point of initial implantation.

To completely arrest the flow of blood in a vessel and to inhibitrecanalization, current methods of coil embolization typically requirethe use of several embolic coils at the target site in the blood vessel.In this “nesting technique”, the embolic coils are deposited within avessel to create a mechanical “plug”. It has been found, however, thatthe use of several coils does not always prevent recanalization of theblood vessel, particularly in larger, high flow vessels. Moreover, itoften takes a relatively long time for the blood vessel to completelyocclude. Therefore, the embolic coils may often migrate into anon-target site prior to vessel occlusion, particularly in larger orhigh flow vessels. Multiple coils are also more expensive than a singlecoil and they require more time to position within the vessel, therebyfurther increasing the cost of the procedure and prolonging thepatient's exposure to the fluoroscope.

Of particular interest to the present invention, the use of monopolarand bipolar radiofrequency devices has been proposed for the occlusionof body vessels from a surrounding lumen or body cavity. For example,U.S. Pat. No. 5,403,311 describes control of vessels bleeding into abody lumen using electrosurgical electrodes which puncture the vesselfrom within a larger lumen enclosing that vessel. Catheters forradiofrequency injury and occlusion of the cystic duct are described inBecker et al. (1989) Radiology 170:561-562 and (1988) Radiology167:63-68 and Tanigawa et al. (1994) Acta Radiologica 35:626-628.Methods and catheters for electrosurgical endovascular occlusion aredescribed in Brunelle et al. (1980) Radiology 137:239-240; Cragg et al.(1982) Radiology 144:303-308; and Brunelle et al. (1983) Radiology148:413-415. Such techniques, however, have not generally been useful inlarge or high flow blood vessels.

For these reasons, it would be desirable to provide improved methods anddevices for endoluminal occlusion of body lumens, and particularly ofblood vessels, for use in the procedures described above. Such methodsand devices should provide effective occlusion of large or relativelyhigh flow body lumens as well as small body lumens. Preferably, themethods and devices will permit the physician to re-access the occlusionsite, to correct recanalization and/or to enhance the occlusion of thissite to prevent subsequent recanalization of the body lumen.

2. Description of the Background Art

Methods and devices for implanting vaso-occlusive elements, such ascoils, in blood vessels and other lumen are described in U.S. Pat. Nos.5,354,295; 5,350,397; 5,312,415; 5,261,916; 5,250,071; 5,234,437;5,226,911; 5,217,484; 5,122,136; 5,108,407; `4,994,069; and 3,868,956;and published PCT applications WO 94/11051; WO 94/10936; WO 94/09705; WO94/06503; and WO 93/06884. Some of the devices described in the abovelisted patents and published applications suggest passing direct currentthrough the element to enhance blood clotting.

Electrosurgical probes for electrosurgical, electrocautery, and otherprocedures are described in U.S. Pat. Nos. 5,405,322; 5,385,544;5,366,490; 5,364,393; 5,281,216; 5,236,410; 4,685,459; 4,655,216;4,582,057; 4,492,231; 4,209,018; 4,041,952; 4,011,872; 4,005,714;3,100,489; 2,022,065; 1,995,526; 1,943,543; 1,908,583; and 1,814,791;and published Japanese application 2-121675; published Germanapplications DE 4139029; DT 2646228; and DT 2540968; and published PCTapplications WO 95/02366 and WO 93/01758.

A method and system employing RF energy for the direct occlusion ofblood vessels and other body lumens are described in co-pendingapplication Ser. No. 08/488,444 filed on Jun. 7, 1995 (attorney docketNo. 16807-3), the full disclosure of which is incorporated herein byreference. See also the patent and publications described in the Fieldof the Invention above.

SUMMARY OF THE INVENTION

Methods and apparatus are provided for deploying vaso-occlusive elementsinto body lumens, such as blood vessels, to occlude a target site withinthe lumen and for enhancing the occlusion of body lumens that alreadyhave vaso-occlusive elements deployed therein. The technique involvesapplying high frequency electrical energy to an electrically conductive,vaso-occlusive element and generating a thermal reaction at the targetsite to damage the luminal wall and induce fibrogenic occlusion of theblood vessel around the vaso-occlusive element. The vaso-occlusiveelement, which is typically an electrically conductive wire coil, helpsreduce blood flow within the vessel and provides a larger surface forenergy transfer between the electrical energy source and the tissue walland surrounding blood. The high frequency electrical energy, typicallyradiofrequency current, is usually sufficient to induce local heating ofthe luminal wall and also to enhance coagulation of the surroundingblood, thereby initiating clotting. The thermally injured wall thencontributes to subsequent fibrosis, thus permanently occluding thelumen.

The vaso-occlusive coil typically has a relatively low electricalresistance so that the high frequency electrical energy flows directlythrough the vaso-occlusive coil to the luminal wall (i.e., withoutsubstantially heating the coil). The electrical energy heats the luminalwall, thereby causing damage and subsequent fibrogenic occlusion of thetarget site. Alternatively, the vaso-occlusive coil may comprisesufficient electrical resistance such that a portion of the highfrequency electrical energy is transferred directly to the coil (ratherthan the luminal wall) to heat the coil and enhance occlusion around thecoil. In this case, the vaso-occlusive coil will preferably have anelectrical resistance slightly less than the tissue wall to ensure thatthe electrical energy flows through at least a substantial portion ofthe coil.

In one aspect, the method comprises contacting a vaso-occlusive coilthat is already deployed at a target site within a body lumen with atleast one electrode and applying the high frequency electrical energy tothe coil in a monopolar or bipolar fashion. Preferably, the energy isapplied in a monopolar mode by contacting the patient's body with asecond, dispersive or return, electrode and then delivering a highfrequency current to the first or active electrode, through at least aportion of the vaso-occlusive coil, the surrounding tissue, and finallyto the second electrode. For bipolar operation, a separate secondelectrode may be provided on the catheter, typically spaced proximallyfrom the first electrode so that it will be located within the bodylumen. The second electrode will usually be spaced a distance of about 2mm to 10 cm from the active electrode.

The first electrode will usually be disposed on the distal end of anintravascular catheter. The catheter can be percutaneously introducedvia well-known procedures and advanced to the target site in a bodylumen in a known manner, typically over a guide wire. The firstelectrode can be engaged against the vaso-occlusive coil in a variety ofways. For example, the electrode (and optionally a pair of electrodesfor bipolar operation) can simply be disposed at a distal location onthe catheter which will contact the vaso-occlusive coil when thecatheter is advanced through the body lumen to the target site.

Alternatively, the electrode may be provided by a separate member, suchas an insulated conventional or specialized guide wire, or a positionerdevice, which may be insulated by the catheter body. In use, theguideline positioner is extended distal to the catheter body, placedagainst the vaso-occlusive coil, and the radiofrequency current isapplied thereto. In the latter case, a distal portion of the positionermay comprise the active electrode, while the return electrode is locatedon the catheter or placed externally on the patient.

In other aspects, the method may comprise deploying the vaso-occlusivecoil at the target site within the body lumen, adjusting the position ofan already deployed vaso-occlusive coil within the target site, orrepositioning the coil to another location in the vasculature. Forinitial deployment, the vaso-occlusive coil will be releasably engagedby the positioner and optionally advanced through the axial lumen of thecatheter for deployment. For repositioning, the coil may be captured bythe positioner and partially or fully retracted into the axial lumen foradjusting coil placement or repositioning the coil to another location.Typically, the coil will be repositioned when previous attempts toocclude a target site have not completely succeeded and the coil is notfixed at the site. A particular advantage of the present invention isthat the coil can be held in place within the body lumen by thepositioner until the high frequency voltage or current has been appliedthereto. Once the voltage has generated a sufficient thermal reaction toinduce spasm and localized edema/narrowing of the vessel (and subsequentfibrogenic occlusion of the lumen) around the coil, the coil will bereleased from the positioner and the positioner removed from thevasculature. In this manner, the fibrogenic occlusion of the bloodvessel will slowly and permanently lock the coil in position at theocclusion site, while the coil is temporarily held in place by the spasmor narrowing of the vessel. This prevents or at least inhibits migrationof the coil downstream through the body lumen after it has been releasedby the positioner.

Devices according to the present invention will generally comprise ashaft having proximal and distal ends and an axial lumen therebetween.For vascular applications, the shaft will typically be a non-conductive,tubular catheter body capable of being introduced to the vascular systemover a guide wire in a conventional manner. A positioner is slidablydisposed within an axial lumen of the shaft and includes a firstelectrode at the distal end for contacting the vaso-occlusive coil. Thepositioner may be a guide wire that is also used for advancing the shaftthrough the body lumen or a separate device inserted into the catheterbody after it has been advanced to the target site. The first electrodeis coupled to a source of high or radiofrequency electrical energy bythe positioner itself, an electrical conductor extending through thepositioner, or through the catheter body.

The positioner preferably comprises a conductive shaft having an outerinsulating sheath extending to a distal portion of the shaft. The distalportion includes an engaging element for releasably engaging thevaso-occlusive coil to either deploy the coil at the target site or toreposition a deployed coil to another location in the patient'svasculature. In one embodiment, the engaging element comprises a pair ofopposed elements which can be selectively opened and closed to engageand release a proximal portion of the coil. Usually, the opposedelements will be openable jaws that are actuated manually with anactuator located on a handle at the proximal end of the positioner. Inanother embodiment, the distal engaging element comprises a plurality ofresilient hooks that are biased away from each other and held togetherby the catheter body. In yet another embodiment, the distal engagingelement comprises a distal pusher element adapted to contact the coiland push it through the catheter body to the target site.

The system of the present invention will also include a second electrodeoperatively coupled to the high frequency energy source. The secondelectrode can be either a second bipolar electrode disposed on thepositioner (usually spaced proximally from the first electrode), thecatheter. or introducing sheath, or a dispersive or return electrodeattachable directly to the patient's skin (where the first or activeelectrode will function in a monopolar manner). The electrodes are thusutilized to apply monopolar or bipolar high frequency energy to thevaso-occlusive coil within the vessel lumen. For example, a separateguide wire could be provided as either a monopolar or one bipolarelectrode.

Frequently, the first electrode(s) will be associated with the distalengaging elements. For example, the opposing jaws or the resilient hookscan also define the treatment electrodes on the positioner. In thebipolar mode, most likely, a separate, second radiofrequency electrodecan be provided on the catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a lumen occlusion system constructed inaccordance with the principles of the present invention;

FIG. 2 is an enlarged perspective view of a distal end of a positionerdevice of the lumen occlusion system of FIG. 1, illustrating a pair ofopposed elements shown in their open configuration;

FIGS. 3A-3D illustrate the use of the system of FIG. 1 and a method forenhancing occlusion of a blood vessel according to the principles of thepresent invention;

FIG. 4 is a sectional view of the distal portion of a second embodimentof a lumen occlusion device, illustrating a method of deploying orrepositioning a vaso-occlusive coil in a body lumen;

FIG. 5 is a detailed, cross-sectional view of the lumen occlusion deviceof FIG. 4, illustrating a plurality of coil-engaging elements releasablyholding the vaso-occlusive coil;

FIG. 6 is a partial sectional view of a third embodiment of a lumenocclusion device constructed in accordance with the principles of thepresent invention; and

FIG. 7 is a partial sectional view of a portion of a lumen occlusiondevice according to another embodiment of the present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The methods and devices of the present invention will be useful forselectively occluding virtually any body lumen that can be occluded witha vaso-occlusive element(s) followed by the application of energy. Whilethe present invention will find its greatest use in the selectiveocclusive of blood vessels, including both arteries, veins, fistulas andaneurysms, it will also find use with other body lumens, such as thefallopian tubes, bile ducts, and the like. The present invention will beparticularly useful for occluding relative large, high flow arteries,veins and vascular malformations, because the present invention presentsa method of releasably holding a vaso-occlusive element(s) until thetarget site of the fluid vessel is partially or completely occluded. Inhigh flow vessels, this effectively prevents the vaso-occlusiveelement(s) from becoming dislodged and migrating downstream of thetarget site.

In the case of blood vessel occlusion, the high frequency electricalenergy will coagulate surrounding fluids, such as blood, and thermallyinjure the intima of the body luminal wall in the occlusion region, thusinitiating a process of thrombosis and fibrosis which will result inrelatively complete vessel occlusion. The high frequency electricalenergy passes through the vaso-occlusive element, which usually takesthe form of an electrically conductive coil, into the body luminal wall.The electrical energy heats the luminal wall, thereby enhancing thethrombogenic and fibrogenic occlusion of the coil at the target site.The vaso-occlusive coil typically has a relatively low electricalresistance so that the high frequency electrical energy flows directlythrough the coil to the luminal wall and surrounding fluid (in fluidcarrying vessels) without substantially heating the coil. The electricalenergy heats the body luminal wall, creating a thermal effect andthereby causing damage and subsequent fibrogenic occlusion of the targetsite. The temperature of the luminal wall will be typically be raised toabout 45° C. to 95° C., preferably about 55° C. to 85° C.

Alternatively, the vaso-occlusive coil may comprise a material havingsome electrical resistance so that a portion of the high frequencyelectrical energy heats the vaso-occlusive coil. In this case, the coilwill preferably have an electrical resistance less than the tissue wallto ensure that the electrical energy flows through at least asubstantial portion of the coil.

Preferably, the energy source will provide radiofrequency electricalenergy, such as that supplied by conventional electrosurgical powersupplies, such as those available from commercial vendors, includingValleylab®, Aspen®, Bovie®, and Birtcher®. The power supply will usuallyprovide energy at frequencies from 200 kHz to 12 MHz, preferably from250 kHz to 500 kHz and may employ a conventional sinusoidal ornon-sinusoidal wave form. The current provided will usually be in therange from about 25 mA to 1 A, preferably from about 50 mA to 250 mAfrom about 5 seconds to 4 minutes, usually from 10 seconds to 1 minute.The actual amplitude and duration of the current will depend primarilyon vessel size, i.e. larger vessels will usually require higher currentsand longer durations.

As discussed in more detail in connection with the specific embodimentsbelow, the RF current may be applied in a monopolar or a bipolar fashionin or near the occlusion region. By “monopolar” it is meant that currentflow will pass between (1) one or more “active” electrodes on theintroducing catheter or the positioner which have surface areas andconfigurations which transfer the energy to the vaso-occlusive coil inorder generate a thermal reaction in the region of the target site; and(2) a “dispersive” or return electrode which is located remotely fromthe active electrode(s) and which has a sufficiently larger area so thatthe current density is low and non-injurious to surrounding tissue. Insome cases, the dispersive electrode may be on the same probe as theactive electrode, and in other cases, the dispersive electrode may beattached externally to the patient, e.g., using a contact pad placed onthe patient's flank.

Bipolar devices according to the present invention will generally employa pair of electrodes in relatively close proximity each having an areaand geometry selected to have a desired physiologic effect on adjacenttissue. In the case of bipolar devices, one or more electrodes will beconnected to one pole of the radiofrequency power supply and will beplaced in contact with the vaso-occlusive coil. The other electrode willbe directly or indirectly in contact with the body luminal wall. Thus,the current flow in the occlusion region will be concentrated throughthe vaso-occlusive coil, then through the luminal wall or through thefluid located between electrode pair(s), rather than from one or moreelectrodes to a remote, dispersive electrode (which is the case inmonopolar operation).

Devices according to the present invention will comprise an introducingcatheter, typically including a shaft having proximal and distal endsand an axial lumen therebetween. For vascular applications, the shaftmay be in the form of a conventional catheter body, typically having alength in the range from 40 cm to 200 cm, usually from 75 cm to 120 cm.The catheter body will usually include means for introducing the bodyover a movable guide wire, typically having a guide wire lumen runningthrough at least a distal portion of the catheter body. Thus, thecatheter body can have either conventional “over-the-wire” design wherea movable guide wire is received through the entire length of thecatheter body or may have a “rapid exchange” or “monorail” design wherethe guide wire is received through a lumen which extends only over adistal length of the body, typically from 5 cm to 25 cm. The catheterbody will have an outside diameter consistent with its intended use,typically being from 1 mm to 5 mm, usually from 2 mm to 4 mm.

The catheter body may be formed from a variety of conventional cathetermaterials, including natural and synthetic polymers, such as polyvinylchloride, polyurethanes, polyesters, polyethylenes,polytetrafluoroethylenes (PTFE's), nylons, and the like. The catheterbodies may optionally be reinforced to enhance their strength,torqueability, and the like. Exemplary reinforcement layers includemetal fiber braids, polymeric fiber braids, metal or fiber helicalwindings, and the like. Optionally, a portion of the catheter body couldbe formed from a metal rod or hypo tube, particularly when the catheterbody is a rapid exchange or monorail design.

The catheter will also include at least one electrode for initiatingradiofrequency current flow, as described above. The electrode may bedisposed on the catheter shaft, may be part of a separate positioner(described below), and/or may be associated with the guide wire used tointroduce the shaft to the body lumen, usually a blood vessel.Configuration of the electrode element will vary depending on whether itis intended to actively contact the vaso-occlusive coil or to functionas a return or dispersive electrode.

The dispersive electrode will typically have a substantially largersurface area, on the order of at least 2 to 3 times larger, than theactive electrode. Active electrodes (the electrode and the occlusivecoil) will typically have relatively small total surface areas,typically being below about 20 mm², usually being below about 10 mm².Dispersive electrodes will typically have a somewhat larger area,typically being greater than 50 mm² for probe-mounted dispersiveelectrodes and greater than 120 cm² for external dispersive pads.

The positioner will generally comprise a shaft that extends through thecatheter body and includes a distal engaging element for releasablyengaging a vaso-occlusive coil. The distal engaging element will alsocomprise the active electrode(s) (or one of a pair of electrodes in thebipolar mode). The engaging element will preferably comprise a holdingor grasping mechanism that holds a proximal portion of the coil fordeploying and/or repositioning the coil within a blood vessel. In thisembodiment, the engaging element will be capable of holding onto thecoil beyond the distal end of the catheter body and/or grasping analready deployed coil for establishing positive electrical contactbetween the engaging element and the coil, repositioning the coil orwithdrawing the coil from the body lumen. Alternatively, the engagingelement may comprise a mechanism for contacting the coil and pushing thecoil through the catheter body. In this embodiment, the coil willgenerally disengage from the engaging element when its proximal endmoves past the distal end of the catheter body. Electrical current maybe re-established by subsequently advancing the positioner to contactthe coil. Specific examples of each of these approaches are described inmore detail in connection with the figures below.

The present invention will generally be useful with virtually any typeof vasoocclusive device or coil that may be endoluminally advanced to atarget site of a body lumen to block fluid passage therethrough. Thevaso-occlusive device will typically be formed from an elongate element,such as a wire, which is extendable from a relaxed, convolutedcondition, to an extended, linear condition in which the wire can beadvanced through the catheter. The vaso-occlusive coil(s) will have arelatively large surface area compared to the electrode to facilitatetransfer of the electrical energy to the tissue wall and surroundingblood. This surface area will usually depend on the size of the coil,which is typically chosen based on the size of the blood vessel. Largervessels will typically require a higher rate of energy transfer due to alarger surface area.

The vaso-occlusive wire generally takes the form of a coil, and may beformed by wrappings or windings of a fine wire comprised of platinum,stainless steel, tungsten, gold or the like. The wire may be coveredwith a fibrous material, such as polyester, to induce thrombus in blood.The wire may be pre-formed so that it adopts a convoluted configurationin a relaxed condition. Alternatively, the vaso-occlusive device may beformed from a flexible pre-shaped polymer tube or rod that is doped withelectrically conducting material so that the rod is more electricallyconductive than the tissue of the body lumen. The convoluted shape ofthe tube or rod may be achieved by a combination of a helical windingand/or irregularities which are imparted during heat treatment, or byshaping the device as it is extruded, before cooling, or by injectionmolding.

Referring now to FIGS. 1-3, a lumen occlusion system 2 according to thepresent invention comprises a shaft in the form of a flexible catheterbody 4 having a proximal end 6 and a distal end 8. A positioner 10includes a flexible shaft 12 sized to extend through catheter body 4 andhaving a proximal end 13 attached to a handle 14. A pair of opposingelements or jaws 16, 17 are attached to a distal end 15 of flexibleshaft 12 for movement between open and closed positions. Once catheterbody 4 has been positioned within a blood vessel of the patient(discussed below), jaws 16, 17 may be introduced through proximal end 6of catheter body 4 and advanced through distal end 8, as shown in FIG.1.

Handle 14 includes an actuator mechanism for opening and closing jaws16, 17. Preferably, the actuator mechanism comprises an inner rod 20slidably disposed within shaft 12 and extending through an inner lumen22 within handle 14. Rod 20 is coupled to a trigger 24 having a leverarm 26 extending through a slot 28 in handle 14. Distal movement oflever arm 26 through slot 28 moves rod 20 in the distal direction,causing jaws 16, 17 to open (see FIG. 2). A spring 30, positionedbetween a bushing 32 within lumen 22 and trigger 24, biases lever arm 26proximally so that jaws 16, 17 are biased into the closed position (FIG.1).

FIG. 2 illustrates a preferred embodiment of the distal end 15 ofpositioner 10.

As shown, jaws 16, 17 are pivotally coupled to each other by a pivot pin60 extending through jaw 17. Jaw 17 has a proximal end portion 62pivotally coupled to a linkage 64 which is, in turn, pivotally coupledto the distal end 66 of rod 20. Proximal movement of rod 20 withdrawslinkage 64 into shaft 12, thereby pivoting proximal end portion 62 ofjaw 17 toward shaft 12. In this manner, distal end portion 70 of jaw 17is pivoted downward towards jaw 16 into the closed position (FIG. 1).Jaw 16 preferably has a recess 72 sized to receive jaw 17 to minimizethe profile of positioner 10 in the closed position. Similarly, distalmovement of rod 20 causes jaws 16, 17 to open (FIG. 2).

In this embodiment, jaws 16, 17 also serve as a common active electrodefor providing radiofrequency current flow in a monopolar procedure.Referring again to FIG. 1, occlusion system 2 further comprises asuitable RF power supply 40 connected to handle 14 via a connection plug42. Jaws 16, 17 are preferably coupled to connection plug 42 throughinner rod 20 and a lead wire 44 within handle 14. Inner rod 20 maycomprise an electrically conducting material or a lead wire (not shown)may extend through an inner lumen within rod 20. Positioner shaft 12will be fabricated from an insulating material to insulate rod 20 fromthe patient. The occlusion system 20 further includes a dispersive orreturn electrode, which is an external dispersive plate 50 coupled to RFpower supply 40 and adapted for mounting on the patient's skin. Ofcourse, the dispersive electrode 50 could be located elsewhere indifferent form (e.g., a sleeve) on the catheter body 4.

FIGS. 3A-3C illustrate use of the lumen occlusion system 2 to enhanceocclusion of a target site TS within a blood vessel BV having one ormore vaso-occlusive coils 100 already deployed at the target site TS.The physician will typically monitor the blood vessel with a fluoroscopeto determine whether the vessel is completely occluded after coil 100has been deployed (or to determine if recanalization has subsequentlytaken place). If the target site is not completely occluded, lumenocclusion system 2 will be used to apply radiofrequency energy to thecoils at the target site to cause thermal damage to the luminal wall(this will induce a fibrogenic reaction). Of course, system 2 can alsobe utilized to deploy the initial coil 100 (or additions to the coil) attarget site TS, as described in more detail in later embodiments.

Referring to FIG. 3A, the distal end 8 of catheter body 4 is introducedtransluminally to a target site TS within a blood vessel BV or otherbody lumen. Typically, a guide wire (not shown) will first be introducedto the target site TS in a conventional manner. Note that positioner 10may also be used as the guide wire, if desired, or positioner 10 may beused without the catheter if no additional coils are necessary. Once theguide wire is in position, the catheter body 4 will be introduced overthe guide wire in a conventional “over-the-wire” manner until the distalend 8 of the body 14 is positioned slightly proximal of thevaso-occlusive coil 100, as shown in FIG. 3A.

After reaching the target site TS, positioner shaft 12 is advancedthrough catheter body 4 until jaws 16, 17 extend beyond distal end 8.Positioner shaft 12 will include an outer insulating sheath 102 proximalto the grasping end to protect the blood vessel wall from electricalenergy delivered therethrough (discussed below). Jaws 16, 17 are openedby moving lever arm 26 (FIG. 1) in the distal direction, as describedabove. As shown in FIG. 3B, positioner shaft 12 will then be advanceddistally until jaws 16, 17 contact a proximal portion of coil 100. Asshown in FIG. 3C, jaws 16, 17 are preferably closed over a portion ofcoil 100 to establish electrical contact between the active electrodes(jaws 16, 17) and the coil and to ensure that this electrical contactremains intact during application of energy to the coil. Aradiofrequency power supply 40 (FIG. 1) applies a radiofrequency voltageto jaws 16, 17 to initiate a radiofrequency current flow between thecontiguous coil 100 and the return electrode 50. The radiofrequencypower supply 40 may be optionally modified to provide an optimumimpedance match. The radiofrequency current flows through coil 100, andthe surrounding blood and the wall of blood vessel BV. The currentthermally damages the blood vessel wall, causing localized swellingaround the coil, as shown in FIG. 3C.

After maintaining the radiofrequency current flow for a desired time andat a desired current level, jaws 16, 17 will be opened to release coil100. The positioner 12 is then withdrawn through catheter body 14. Atthe time of device removal, the blood vessel will be thrombosed andtotally or mostly occluded. Subsequent fibrosis of the thrombus willmake the occlusion substantially permanent.

A second embodiment 110 of the lumen occlusion system of the presentinvention is illustrated in FIGS. 4 and 5. System 110 is similar tosystem 2 in that it includes a proximal handle and an external,dispersive electrode coupled to an RF power supply (see FIG. 1). Thesystem 110 differs from system 2, however, in that it includes aplurality of resilient hooks 112-114 for grasping vaso-occlusive coil100 and delivering a radiofrequency current thereto. As shown in FIG. 4,a positioner shaft 116 has a proximal end (not shown) connected to theproximal handle, a distal end 118 and an axial lumen 119. An inner rod120 is slidably positioned within axial lumen 119 and connected to anactuator mechanism (not shown) on the proximal handle.

Resilient hooks 112-114 are connected to the distal end of rod 118 andbiased outward into a spaced apart configuration (not shown). When hooks112-114 are completely or partially (FIGS. 4 and 5) withdrawn into shaft116, the inner wall 122 of shaft 116 urges the hooks 112-114 towardseach other. One or more of the hooks 112-114 is also an active electrodefor delivering RF energy to coil 100. To that end, positioner shaft 116includes an electrical conductor, such as a wire (not shown) extendingthrough rod 118 to couple active electrode 112 with the RF power supply.

Occlusion system 110 can be used for deploying vaso-occlusive coil 100at a target site TS in a blood vessel BV and for deliveringradiofrequency energy to coil 100 to enhance fibrogenic occlusion of thetarget site TS. In use, hooks 112-114 are moved proximally outwardbeyond the distal end of positioner shaft 116 so that they are spacedapart from each other. The coil 100 is then positioned between hooks112-114 and the hooks are partially withdrawn into shaft 116 so that theinner wall (not shown) of shaft 116 urges the hooks 112-114 together tograsp coil 100 (this partially withdrawn position is depicted in FIGS. 4and 5). Positioner shaft 116 and coil 100 are then advanced throughcatheter body 4 to the target site (the distal end 8 of catheter body 4is positioned at the target site as described previously). The innerwall 122 of cathetor body 4 facilitates the interlock between hooks112-114 and coil 100 during movement through the catheter body.

Once coil 100 is advanced beyond the distal end 8 of catheter body 4, itwill begin to relax into a convoluted configuration for occlusion ofblood vessel BV, as shown in FIG. 4. Positioner shaft 116 is advanceduntil at least a portion of coil 100 or the entire coil and the hooks112-114 extend beyond the distal end 8 of catheter body 4 (FIG. 5). AnRF voltage is then delivered through active electrode or hooks 112-114to the coil to generate thermal damage within blood vessel BV and inducesubsequent fibrogenic occlusion of the blood vessel (as discussedpreviously). Since coil 100 is held in position by hooks 112-114, itwill not migrate from TS during the occlusion process. Once the targetsite is damaged, localized swelling and thrombosis fixes coil 100 inplace. Rod 120 is then moved distally to expand hooks 112-114 andrelease the coil 100. Rod 120 is typically biased proximally to a closedhook position. The positioner 116 and catheter 4 can then be removedfrom the patient's vasculature.

After the occlusion system has been removed from the blood vessel BV, asecondary RF treatment may become necessary if, for example, the targetsite is not sufficiently occluded. In this case, the occlusion systemwill be re-inserted as described above to re-access the occlusion coil100, to recouple the coil to the RF electrode and to deliver additionalRF energy to the target site.

FIGS. 6 and 7 illustrate bipolar embodiments of the present invention.Referring to FIG. 6, a positioner 150 comprises a flexible shaft 152extending through catheter body 4 as in the previous embodiments.Positioner 150 includes one bipolar electrode in the form of a disc 154disposed at the distal end of shaft 152. Disc 154 is electricallycoupled to the RF power source by an inner conductive wire 156 extendingthrough shaft 152. Shaft 152 is contained within an electricallyconductive sheath proximal to its distal end to form a second electrode158. Second electrode 158 is coupled to RF power source 40 by a secondinner conductive wire 160 that extends through shaft 152 and iselectrically insulated from wire 156. Note that second electrode 158 isschematically illustrated in FIG. 6 and may be larger than that shown.Second electrode 158 will preferably have a larger surface area thandisc 154 and coil 100 to minimize tissue damage at the second electrode.

In use, positioner shaft 152 is advanced beyond the distal end ofcatheter body 4 so that active electrode disc 154 contacts thevaso-occlusive coil 100 deployed at the target site TS within bloodvessel BV, as shown in FIG. 6. Electrode disc 154 may also be used as apusher to deploy coil 100 by pushing the coil through catheter body 4.RF voltage is applied between electrode 158 and electrode 154 so that anRF current is initiated therebetween. Since the coil is more conductivethan tissue, the RF current flows through at least a portion of coil100. The surrounding blood and other fluids provide a path for the RFcurrent from coil 100 and electrode 154 to electrode 158. The RF currentwill be sufficient to coagulate blood and to generate thermal damage tothe intima of the tissue wall to enhance the occlusion of target siteTS.

Referring to FIG. 7, another embodiment of positioner 170 comprises ashaft 172 and a pair of jaws 174, 176 extending from a distal end ofshaft 170. Similar to previous embodiments, positioner 170 includes aninner rod 178 slidably disposed within shaft 172 and coupled to aproximal actuator (not shown) for opening and closing jaws 174, 176. Inthis embodiment, first jaw 174 and a distal portion 180 of second jaw176 are the first electrodes. The second electrode 158 is disposedproximal to the first electrodes 174, 176, similar to FIG. 6. The jaws174, 176 and second electrode 158 are each coupled to an RF power sourceby inner conducting elements 184, 186, respectively, which can comprisewires, rods or the like. RF voltage is applied between jaws 174, 176 andsecond electrode 158 to initiate RF current therebetween (via the coil).

Although the foregoing invention has been described in some detail byway of illustration and example, for purposes of clarity ofunderstanding, it will be obvious that certain changes and modificationsmay be practiced within the scope of the appended claims.

What is claimed is:
 1. A lumen occlusion system, comprising: a source of high frequency electrical energy; an introducer having a shaft with proximal and distal ends and an axial lumen therebetween; a positioner disposed within the axial lumen and having a shaft and a distal engaging element for contacting a vaso-occlusive element at a target site within a body lumen, the distal engaging element comprising a first electrode coupled to the source of high frequency electrical energy; and a second electrode coupled to the source of high frequency electrical energy wherein the distal engaging element has an opened and closed configuration, and the positioner is slidable relative to the introducer to close the distal engaging element when the distal engaging element is unconfined outside the axial lumen of the introducer.
 2. The system of claim 1 wherein the distal engaging element comprises means for advancing the vaso-occlusive element through the axial lumen of the introducer to a target site in a body lumen.
 3. The system of claim 1 wherein the distal engaging element comprises a holding member for releasably holding a portion of a vaso-occlusive element.
 4. The system of claim 1 wherein the holding member is configured to releasably hold the vaso-occlusive element beyond the distal end of the introducer.
 5. The system of claim 1 wherein the second electrode comprises an external dispersive electrode adapted for engaging an external portion of the patient's body.
 6. The system of claim 1 wherein the second electrode is a return electrode coupled to the introducer shaft, the return electrode being spaced from and electrically insulated from the first electrode.
 7. The system of claim 1 wherein the first and second electrodes are located on the distal engaging element and the positioner shaft for initiating current therebetween.
 8. The system of claim 1 wherein the introducer is a flexible shaft having dimensions suitable for introduction to a patient's vasculature.
 9. The system of claim wherein the source of radiofrequency energy is configured to apply radiofrequency energy at a frequency of at least 200 kHz to the vaso-occlusive element.
 10. A lumen occlusion system, comprising: a source of high frequency electrical energy; an introducer having a shaft with proximal and distal ends and an axial lumen therebetween; a positioner disposed within the axial lumen and having a shaft and a distal engaging element for contacting a vaso-occlusive element at a target site within a body lumen, the distal engaging element comprising a first electrode coupled to the source of high frequency electrical energy; and a second electrode coupled to the source of high frequency electrical energy; wherein the distal engaging element comprises a plurality of opposed members movable between open and closed positions, at least one of the opposed members comprising the first electrode.
 11. The system of claim 10 wherein the positioner further includes a proximal actuator for opening and closing the opposed members.
 12. The system of claim 10 wherein the opposed members are biased towards each other.
 13. A lumen occlusion device for use with a source of high frequency electrical energy comprising: an introducer having a shaft with proximal and distal ends and an axial lumen therebetween; a positioner slidably disposed within the axial lumen and having a distal engaging element for releasably engaging an electrically conductive vaso-occlusive element at a target site within a body lumen, the distal engaging element comprising an electrode; and an electrical conductor for coupling the electrode to the source of high frequency electrical energy wherein the distal engaging element has an opened and closed configuration, and the positioner is slidable relative to the introducer to close the distal engaging element when the distal engaging element is unconfined outside the axial lumen of the introducer.
 14. The device of claim 13 wherein the distal engaging element comprises means for releasably holding the vaso-occlusive element in contact with the electrode beyond the distal end of the introducer.
 15. The device of claim 13 wherein the distal engaging element comprises a distal surface sized to engage the vaso-occlusive element and to push said element through the axial lumen of the introducer, the vaso-occlusive element being released from the distal surface of the engaging element when the vaso-occlusive element is pushed beyond the distal end of the introducer shaft.
 16. The device of claim 13 wherein the distal engaging element comprises a plurality of opposed elements movable between open and closed positions, at least one of the opposed elements comprising the first electrode.
 17. The system of claim 16 wherein the positioner further comprises a proximal actuator for opening and closing the opposed elements.
 18. The system of claim 16 wherein the opposed elements are biased towards each other.
 19. The device of claim 13 wherein the introducer is a flexible catheter. 